The Biomechanics Core will provide technical and personnel support for Projects #1, 2 and 4. The Biomechanics Core will provide facilities, personnel, and equipment commonly used by several projects. The Biomechanics Core will be composed of 3 Core units: (1) In vitro Biomechanics; (2) Finite Element Modeling and (3) In vivo Biomechanics. The In vitro Biomechanics Core Unit will focus on testing of biological tissues at the macro and micro level. These experiments are necessary to achieve the goals of Projects #1, 2 and 4. The Finite Element Modeling Core Unit will maintain and upgrade the computer facilities to maximize the computing power required for dealing with more realistic spine models (e.g. modeling the poroelastic behavior of the disc proposed in Project #2). This unit will also perform various finite element analyses in support of Projects #1 and #4 by providing the information on the stress-strain distributions in the subjects? and engineered discs that are necessary for better interpretation of measured results but impossible to measure experimentally. The In Vivo Biomechanics Core Unit will be used to obtain data on in vivo spinal. This unit will also manage the participation of human subjects (particularly Project # 1). We intend to centralize these Core Units into one Core facility directed and co-ordinated by one person to guarantee the most effective and efficient integration of research approaches. The coordination of the Core Units with the individual research Projects creates more flexibility and efficiency in allocating laboratory, technical and personnel.